Twincat system error

I am doing a project on twincat 2.11 with CX-1020 controller which doesnt support Twincat 3. I can connect the PC to PLC and also able to upload the system configuration from the controller but the programm which is present in the controller is not accessible.I tried to to upload the program from target PLC to PC but it is showing an error that the 'Runtime is already in use' or 'source file could not be read'.The runtime port 801 is also selected in the PLC control setting but still the error is comming.I also added the multiple runtime ports but its not showing while uploading.Kindly provide me the solution for this.

In 2.11 it is not possible to upload a program from PLC, Only when ou have saved the source on the PLC you can do this.

The 'Runtime is already in use' can occur if another computer is logged into TwinCAT. This is because TwinCAT will only allow one PC at a time to be logged into the runtime. This can also occur if someone was logged in and did not properly logout, but it will clear up after a period of time.

I have also seen a couple controllers get locked into that state and the only solution was to cycle the power on the controller.

As shooter also mentioned, you will only be able to upload the program if the previous programmer downloaded the source code to the controller.